Protective circuits



Nov; 22, 1927. 1,649,884. s. B. WRIGHT PROTECTIVE CIRCUlIS Filed Sept. 26, 1924 EIVMVENTOR ATTORNEY Patented Nov. 22, 1927.

UNITED STATES PATENT OFFICE.

SUMNER B. WEIGHT. OF EAST ORANGE. NEW JERSEY, .AE-SIGNOB AMERICAN TELE- PHONE AND TELEGBAPH COMPANY, A COREORATION OF NEW YORK.

PROTECTIVE CIRCUITS.

impressed, which high or peak voltages might be detrimental to apparatus associated with the circuit.

The protective arrangements; of the invention consist of an amplifier-detector-relay combination associated with the trans mission circuit which will operate to disable the circuit when the peak values of the impressed voltage exceed a certain predeten mined amount. By means of such an arrangement it is possible to materially reduce 7 the operation of other protective devices.

such as circuit breakers usually associated with vacuum tubes in the circuit, or fuses or similar devices.

It is usually the practice to associate some form of circuit breaker device with the vacuumtube apparatus in a circuit, the purpose of such device being to prevent the blowing out of the tubes due to local disturbances therein or to disturbances caused by incoming voltages that are above desired limits. 'The operation of a device of this type causes considerable loss of circuit time as several minutes may be needed to readjust and restore the tube apparatus to normal. In the ordinary voice current there may exist peak voltages or momentary impulses that are high enough when subjected to the normal amplification of the system to cause these circuit breaker devices to operate. Such peaks might be caused by the talker coughing or other unusual vocal disturbance. Peak voltages caused in this manner would only be momentary, or of very short duration, but if they were allowed to reach the vacuum tube apparatus they would nevertheless operate the circuit breaker thereat and cause the loss of much circuit time. Hence the protective device of this invention is'provided on the input side of the vacuum tube apparatus to out out and eliminate or reduce all of these peak voltages; before they reach the vacuum tube appara-' tus thus saving considerable circuit time and inconvenience. of the invention will appear more fully from the following detailed description of its operation.

The invention may be more fully understood from the following description together with the accompanying drawing in Other features and objects T V Application fil ed September 28, 1324. serial .No. 740,109.

the figure of which is illustrated a circuit diagram of a preferred'form of the invention. I

' In the drawing the protective device of the invention is illustrated as applied to a radio transmitter circuit. An antenna 14 is shown connected through a transformer 13 to a circuit. including a vacuum tube amplifier 10. The plate circuit of the amplifier 10 is connected through the winding of a marginal relay 11 and thence over its contact to the source of supply of the plate, or B voltage 12. The marginal relay 11 will operate asa circuit breaker when the impressed voltages exceed a desired limit or when local currents in the tube apparatus become too great and will break theplate current circuit and stop-the operation of the vacuum tube by cutting oil? the Bvoltage. The input of the vacuum tube 10 is connected by a transformer 9 to a line L. Included in the line L is a variable artificial line 1, or any suit able device for controlling the volume of the energy applied to the tube 10. Associated with line L between device 1 and the input of the vacuum tube apparatus is the pro.- tectivecircuit' of this invention. I

The voice energy coming in over line L is transmitted through the device 1 which is controlled by an operator who endeavors to maintain a uniform level of energy at the output of device 1. It is obviously imposthrough the transformer 3 to the amplifier.

4, and thence to the detector 5 and thence to the marginal relay 6. The sensitivity of this protective circuit will be adjusted so that relay 6 will not operate on the ordinary energy of the voice current transmitted but will operate on energy above that, such as would be encountered from these peak volt ages. These peak voltages accordingly will cause operation of relay 6 which will thereupon close thenormally open circuit 7 and thus disable the transmission circuit L so that these peak voltages will not/be transmitted to the amplifier apparatus 10 and will not afiect the circuit breaker 1.1,. v Obvia ously these peaks of voltage or bursts of I energy are of very short duration and hence the relay 6 will be operated and the line L disabled only momentarily rather than the much. longer period which would ensue if the circuit breaker 11 were operated As soon as these peak voltages die out the line is restored to normal again.

The contacts of the relay 6 are shown in the drawing asnormally open and the disabling process is accomplished by applying a short circuit to the transmission line L. Normally closed contacts which interrupt transmission by breaking thetransmission circuit might; however, be utilized equally well. The relay 6 might also be utilized to introduce a loss in the transmission line to counteract these peak voltages if desired rather than to control a complete disabling action" such as the short circuit arrangement shown; The relay 6 should be adjusted to operate fasterthan the circuit breaker 11 for the device to be efiect'ive in saving the operation of the circuit breaker and thereby preventing loss of circuit time. Of course, there will be a short period corresponding to' the time of operation of relay 6, during which the peak value will exist beyond the protective circuit. In order to eliminate this period and thereby even more completely protect the vacuum tube apparatus from the effects of these peak voltages a delay circuit 15 of any well known type might be inserted inthe line L as shown between circuit 2 and circuit 7 If adelay circuit were used as shown and the delay was equal to or greater than thetime of operation of relay 6, then absolutely no energy greater than the predetermined value could get into the vacuum tube; apparatus. I

l/Vhile the invention has been illustrated as associated with a radio transmitter its use is not so limited but it may be utilized In any type of transmission circuit utilizing a rangements of which a circuit breaker might he a part. Accordingly, while the in vention has been disclosed in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many and widely varied form without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

ii. A. transmission line over which voice currents are transn'iitted, a translating device in said line protective device associated with said translating device. a protectivecircuit associated with said line on the input side of said translating device, said protective circuit including an amplifier, a detector, and a relay adjusted to operate on voltages other than those usually encountered in the voice range, and means-controlled by said relay for disabling said transmission circuit. ,7 7 .7

2'. A transmission line over which currents within a certain vvoltage range are being transmitted, amplifying apparatus in said line, a circuit breaker associated with said amplifying apparatus to protect saidfappa ratus from voltages outside of said range, a protective device associated with said line on the input side of said amplifying apparatus, said protective device comprisingan input circuit and an output circuit bridged across said line, a delay circuit included in said line between said input and output circuits, and means in said protective, device responsive to voltages outside of said range for preventing said last mentioned voltages from being transmitted to said amplifying apparatus. v r

In testimony whereof, I have signed my name to this specification this 25th day of September, 1924. y I H v SUMNER B. \VRIGHTQ 

